Sausage casings of regenerated cellulose are well known in the art. These casings are formed by extruding regenerated cellulose into tubes or by coating a roll of paper with viscose and then regenerating the cellulose. The casing thus formed is then further treated for sale to a customer. For example, the casing is moisturized to permit its stuffing without the need for soaking the casing. The casing also can be provided with various coatings to facilitate its use in stuffing and subsequent processing operations. Typical coatings applied to the casings include moisture and/or oxygen barriers and liquid smoke.
For some stuffing operations the casing is supplied to the customer in a shirred form. For other stuffing operations the casing is supplied in the form of rolled flat stock. To insure a continuous stuffing operation, the casing, whether supplied in shirred form or as roll stock, should be a continuous casing length. Shirred casing usually is not supplied in lengths greater than about 300 feet whereas a roll of flat stock may contain upwards of fifteen hundred (1500) feet or more of casing.
Providing a roll of casing containing upwards of 1500 feet of casing presents a problem due to the difficulty in making a single casing length of the relatively long length required for roll stock. This is because the casing may break during manufacture or a defect may appear in the casing which must be removed. This results in lengths shorter than the whole multiple length of casing needed for each roll. Short lengths can be spliced together to provide the whole multiple length of casing desired, but splices generally are considered undesirable and preferably are voided. For example, it is difficult to provide a splice which is not degraded over time by moisture, liquid smoke or other casing constituent and which is able to withstand the rigors of the stuffing operation. Accordingly, it is not unusual for a casing manufacturer to discard less than whole multiple lengths of casing or use them for other purposes rather than provide the customer with a roll of casing containing one or more splices.
A typical stuffing operation using roll stock puts a considerable strain on the casing. The flat casing from the supply roll is laced over a series of feed rolls including one or more dancer rolls and then it is opened and fed onto the stuffing horn. Periodically during the stuffing operation, the dancer roll impacts the flat casing. This subjects the casing to sudden and violent tensile stresses. Several impacts may occur in the vicinity of each splice. If the splice fails, the machine must be shut down and the casing relaced through the feed and dancer rolls.
The splice also is subjected to a more sustained tensile stress when the casing is pulled taut to gather it about the ends of the stuffed product during a closing operation. Thus, it is important that the splice be strong enough to withstand the rigors of stuffing so as to avoid a production interruption caused by splice failure.
Heretofore, one splice technique involved simply telescoping or butting the ends of the casing to be joined and then wrapping the joint with a pressure sensitive adhesive tape. This method is described as prior art in U.S. Pat. No. 4,032,176. A taped splice described as prior art in the U.S. Pat. No. 4,032,176 is not suitable for use in stuffing operations because moisture or other casing constituents weaken the splice over time and cause it to fail when subjected to the rigors of a stuffing operation.
If the tape backing has a low tensile strength it may fail under the impact of the dancer rolls or under the sustained tensile stress of the gathering/clipping operation. If the backing is strong enough to withstand these stresses, then the impact of the dancer rolls or the longitudinal strain of gathering and clipping causes the tape adhesive to fail. Failure of the adhesive is not uncommon because moisture in the casing beneath the tape weakens the adhesive bonding. It also should be appreciated that, as set out hereinabove, the casing may be coated or impregnated with other materials such as liquid smoke which also tend to weaken or prevent a pressure sensitive adhesive bonding.
Prior art publications such as U.S. Pat. Nos. 4,391,302 and 4,610,742 disclose that pressure sensitive adhesives are not suitable for casing splices and that high strength splices require a curing of the adhesive bond with a combination of heat and pressure. While such splices may be sufficient to withstand the rigors of stuffing, they require special equipment and are time consuming and inconvenient to fabricate on the production line during the manufacture and rolling of the flat casing.
Accordingly, there is a need for an improved spliced casing article and splicing method. In particular, there is a need for a casing splice and splicing method utilizing a pressure sensitive adhesive tape for joining casings wherein the casings are premoisturized to at least about 20% moisture based on the total weight of the casing and wherein the casings may be coated or impregnated with other constituents, such as liquid smoke, that may resist or inhibit pressure sensitive adhesive bonding.
Failure of casing splices made with pressure sensitive adhesive tapes occurs in either of two modes. In one mode the tape backing fails when a casing is subjected to a tensile stress. That is, the adhesive doesn't fail, but the tape backing tears so that portions of the tape remain adhered to each of the separated casing ends. In a second mode, the tape backing remains intact but the adhesive fails so that the tape pulls free from one of the casing ends. This type of splice failure is observed even though the tape has an adhesive which exhibits good adherence to the moisturized cellulosic casing.
Close examination of splice failures of the second mode establishes that the failures initiate at the lateral edges of the tape transverse the longitudinal axis of the casing and particularly at points along these edges where the tape has lifted or separated from the casing. Once the lateral edge of the tape has lifted from the casing, tensile stresses (as caused, for example, by a dancer roll impacting against the casing or by gathering and closing the casing) cause the tape to peel rapidly from the casing in a direction parallel to the longitudinal axis of the casing. Failure is a peeling-type failure or "adhesive" failure rather than a "cohesive" failure. "Cohesive" failure as used herein means a shear failure of the tape adhesive so that portions of the adhesive remain adhered to both the casing and the tape backing after the splice fails. In contrast with cohesive failure, a "peeling type" failure or "adhesive" failure as used herein means a failure which results when an edge of the tape peels from the casing so that the tape adhesive remains intact on the tape backing and little or none of the adhesive remains on the casing. In general, less force is required to cause an adhesive failure than to cause a cohesive failure. It has been observed that once a lateral edge of the tape begins to lift or is separated from the casing, peeling or adhesive failure progresses very rapidly.
Splices of prior art U.S. Pat. Nos. 4,391,302 and 4,610,742 exhibit relatively high peel strengths because heat and pressure are used to cure a bond between the casing and the splice material. However, it is an object of the present invention to provide a casing splice and splicing method which uses a pressure sensitive adhesive tape for joining lengths of cellulosic casing without heat and pressure curing of the adhesive bond.